Sometimes, just getting more air and fuel in and more exhaust out of the GY6 is how you want to make power, rather than feeding more into the cylinder just to cram it in with the stock sized valves. With big 28/23 valves, getting more in will stuff the cylinder with more air and fuel to burn while at the same time the bigger exhaust will allow that used up mixture to get out faster. This can result in more torque over more power. The Taida GY6 Big Valve Head is available for the 54mm Standard A-Cases